using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;

/// <summary>
/// SystemController singleton
/// </summary>
public class SystemController
{
    /// <summary>
    /// The instance controlling the singleton
    /// </summary>
    private static SystemController instance = null;

    /// <summary>
    /// Stack of the loaded scenes, used to easily go back to previous scenes
    /// </summary>
    private Stack<int> sceneStack = new Stack<int>();

    /// <summary>
    /// Index of the previous loaded scene
    /// </summary>
    public int previousScene = -1;

    /// <summary>
    /// Index of the current loaded scene
    /// </summary>
    public int currentScene = -1;

    /// <summary>
    /// Get the instance loaded by the singleton
    /// </summary>
    /// <returns>SystemController instance</returns>
    public static SystemController GetInstance()
    {
        // Create a new instance if non exists
        if (instance == null)
        {
            instance = new SystemController();
            instance.currentScene = SceneManager.GetActiveScene().buildIndex;
            instance.sceneStack.Push(instance.currentScene);
        }
        return instance;
    }

    /// <summary>
    /// Get the number of passively 'active' scenes
    /// </summary>
    public int GetSceneStackSize() { return sceneStack.Count; }

    /// <summary>
    /// Load the scene and push on the stack
    /// </summary>
    /// <param name="scenePath">Path of the scene</param>
    public void LoadNextScene(string scenePath)
    {
        LoadNextScene(SystemController.GetSceneIndex(scenePath));
    }

    /// <summary>
    /// Get the index of a given scene
    /// </summary>
    /// <param name="scenePath">Path of the scene</param>
    /// <returns></returns>
    public static int GetSceneIndex(string scenePath)
    {
        return SceneUtility.GetBuildIndexByScenePath(scenePath);
    }

    /// <summary>
    /// Load the scene and push on the stack
    /// </summary>
    /// <param name="sceneIndex">Buildindex of the scene</param>
    public void LoadNextScene(int sceneIndex)
    {
        previousScene = currentScene;
        currentScene = sceneIndex;

        sceneStack.Push(currentScene);
        SceneManager.LoadScene(currentScene);
    }

    /// <summary>
    /// Swap the current scene with the new scene on the stack
    /// </summary>
    /// <param name="scenePath">Path of the scene</param>
    public void SwapScene(string scenePath)
    {
        SwapScene(SystemController.GetSceneIndex(scenePath));
    }

    /// <summary>
    /// Swap the current scene with the new scene on the stack
    /// </summary>
    /// <param name="sceneIndex">Buildindex of the scene</param>
    public void SwapScene(int sceneIndex)
    {
        currentScene = sceneStack.Pop();
        LoadNextScene(sceneIndex);
    }

    /// <summary>
    /// Go back to the previous scene and unload the current scene
    /// </summary>
    public void BackToPreviousScene()
    {
        previousScene = sceneStack.Pop();
        if (sceneStack.Count > 0) SceneManager.LoadScene(currentScene = sceneStack.Peek());
        else Application.Quit();
    }

    /// <summary>
    /// Go back to a specific scene, unloading all the scenes on the way
    /// </summary>
    /// <param name="scenePath">Path of the scene</param>
    public void BackToScene(string scenePath)
    {
        BackToScene(SystemController.GetSceneIndex(scenePath));
    }

    /// <summary>
    /// Go back to a specific scene, unloading all the scene on the way
    /// </summary>
    /// <param name="sceneIndex">Buildindex of the scene</param>
    public void BackToScene(int sceneIndex)
    {
        previousScene = currentScene;
        while (0 < sceneStack.Count && sceneStack.Peek() != sceneIndex) sceneStack.Pop();

        if (sceneStack.Count > 0) SceneManager.LoadScene(currentScene = sceneStack.Peek());
        else Application.Quit();
    }
}